Spinning fuzes,in particular for small caliber shells



June 17, 1969 i w. GUERNE 3,450,048

SPINNING FU ZES, IN PARTICULAR FOR SMALL CALIBER SHELLS Fiied March 13, 1967 United States Patent 5 Int. Cl. 1 42c 15/22 vs. Cl. 102-79 7 Claims ABSTRACT OF THE DISCLOSURE A spinning shell fuze includes a body and a firing pin slidable axially in said body. To prevent axial sliding of said firing pin before the projectile is launched, a strip is spiral wound about a sleeve freely rotatable about said firing pin. This spiral wound strip bears through its edges on the one hand against a shoulder of the fuze body and on the other hand against a flange belonging to said sleeve, said flange bearing against a shoulder of the firing pin so that said sleeve is driven axially by said firing pin when the latter is actuated by the impact of the shell against an obstacle.

The present invention relates to spinning fuzes, this term designating the fuzes intended to be fitted on spinning shells which are armed (that is to say made sensitive to a possible impact) by the centrifugal force brought into play by the spinning movement of the shell. The invention is more especially concerned with small caliber shells, in particular of a caliber ranging from 20 to 50 mms.

The chief object of the present invention is to provide a fuze of this type which is better adapted to meet the requirements of practice than those known up to this time, especially from the point of view of safety.

The fuzes with which this invention is concerned comprise a movable axial element (.generally a firing pin) capable of igniting, by an axial displacement thereof, the fuze primer, said movable element being prevented from moving, before the shot is fired, by a centrifugal locking device releasable by the radial acceleration produced by the spinning of the shell and comprising a spiral wound strip, generally metallic, a coaxial with said element and adapted to play, through one of its edges, before the shot is fired, that is to say when, the strip is still wound, the part of an axial holding abutment preventing displacement of said movable element, whereas after the shot has been fired and once said spiral strip has been unwound as far as permitted by the radial dimensions of its housing, it permits axial displacement of said movable element which is to ignite the fuze primer.

According to the present invention, instead of winding this spiral strip directly on the movable element to be locked, the fuze further comprises a sleeve interposed between said spiral strip and said movable element and mounted in such manner as to be able to rotate freely with respect to said movable element, the whole of the spiral strip and the sleeve being arranged in such manner that said spiral strip, when it is unwinding, drives the sleeve in rotation, whereby the unwinding of said spiral strip is braked by the angular inertia of the sleeve, this braking of the spiral strip unwinding movement delaying the release of the movable element and thus increasing the safety of the fuze, i.e. the distance from the gun muzzle for which the fuze is armed.

Preferred embodiments of the present invention will be hereinafter described with reference to the appended drawings, given merely by way of example, and in which:

FIG. 1 is an elevational view, partly in axial section, of a point detonating fuze made according to the present invention;

FIG. 2 is a cross section, on the line II-II of FIG. 1, of the locking means of this fuze;

FIG. 3, is an elevational view, partly in section, of a base detonating fuze made according to this invent-ion.

The fuze according to this invention illustrated by FIGS. 1 and 2 includes a fuze body 1 in which is slidable an axial firing pin 2 adapted to cause, by axial displacement thereof toward the rear, the firing of a primer (not shown by the drawing) housed in the rear portion 1a of the fuze body.

The centrifugal locking device includes a spiral strip 3 wound about the axis of firing pin 1 and the front edge of which acts as an abutment for holding firing pin 1 in inoperative position. On the drawings the spires formed by strip 3 have been shown as being not in contact with one another, but this is merely for the sake of clarity and, actually, the spires of the strip adjoin one another.

Once strip 3 has been unwound within the limits permitted by the radial dimensions of its housing 4, strip 3 permits the axial displacement of firing pin 1 so as to operate the fuze.

Advantageously, as shown, spiral wound strip 3 is surrounded by an expansible slit ring 5 for keeping said strip in the wound position until the shot is fired. Upon firing of the shot this ring 5 is expanded by the centrifugal force against the wall of housing 4, thus releasing spiral wound strip 3 which can then unwind under the action of the centrifugal force.

According to the present invention, as illustrated by FIGS. 1 and 2 instead of winding spiral strip 3 directly on firing pin 2, there is provided a sleeve 6 interposed between strip 3 and firing pin 2 and freely rotatable about said firing pin, the whole formed by spiral wound strip 3 and sleeve 6 being such that, when spiral strip 3 unwinds under the action of the centrifugal force, it drives sleeves 6 together with it.

The connection between spiral strip 3 and sleeve 6 is such that, at the end of the unwinding of said strip, the inner end thereof releases sleeve 6 so as to permit axial movement of the whole of firing pin 2 and sleeve 6.

For this purpose, advantageously, as shown by FIG. 2, the inner end 7 of strip 3 is U-bent and engaged in a groove 7a provided in the outer wall of sleeve 6 and parallel to the generatrices thereof.

Advantageously strip 3 is made as thin as possible, account being taken of the stresses to be exerted thereon, whereby, for a given area of its end edges in the wound position, it has the greatest possible number of spires, the time necessary for the unwinding of such a spiral strip being the greater as it comprises a greater number of spires.

For instance strip 3 may be cut from a thin metal sheet (such as a foil) for instance of bronze or steel.

As for sleeve 6 it preferably has an angular inertia as high as possible, account being taken of the strength of the strip. For instance sleeve 6 is made of brass.

Sleeve 6 may consist of a mere cylindrical piece, possibly provided with holes or slots. It seems preferable to make it as shown by FIG. 1 where sleeve 6 comprises a cylindrical portion mounted with an easy fit on firing pin 2 and provided with a flange 6a on the side thereof where is located the active edge of spiral spin 3. Said flange 6a is interposed between said edge of strip 3 and a shoulder 2a of firing pin 2.

Preferably flange 6a has an outer diameter such that the whole active edge of strip 3 bears thereon. Flange 6a might include a cylindrical projection extending toward the fuze nose.

I As sleeve 6 must move together with firing pin 2 durmg each rearward displacement, said sleeve is advantageously made of a height such that the end 6b thereof opposed to flange 6a engages in a guiding bore 8.

It should be noted that, in order to reduce friction in guiding bore 8, sleeve 6 might be made of an external diameter smaller than the diameter of said bore, a guiding ring fitted on firing pin 2 being provided near the end 6b of said sleeve.

By way of example and without involving any limitation in the construction of the fuze according to the present invention, it is pointed out that, in an embodiment according to FIGS. 1 and 2 for a 20 mms. caliber shell the dimensions were as follows:

Spiral strip 3 was made of bronze foil, this strip being 580 mms. long, 3 mms. high and 0.05 mm. thick, its weight being 0.76 gr. and the number of spires when the strip is wound being 36.

Sleeve 6, made of brass, had a total height of 5.8 mms. and a weight of 0.54 gr.

The safety from the gun muzzle averaged 20 meters for an initial velocity of about 1,050 meters and a spinning rate averaging 87,000 revolutions per minute.

Now, if the invention is applied to a base detonating fuze, the construction is similar with the difference that firing pin 2, instead of being mounted in the front part of the fuze and of having its pointed end directed toward the rear, is mounted in a base plug 9 and has its point directed toward the front, as shown by FIG. 3. The reference numerals in FIG. 3 are the same as in FIGS. 1 and 2.

The operation of a fuze according to the present invention as illustrated by the appended drawings results clearly from the above description.

A spinning fuze according to this invention has many advantages, and in particular the following ones:

Its construction is simple due to the fact that the spiral wound strip acts as a centrifugal locking means, making it unnecessary to provide a special locking member independent of the strip. Therefore the construction is cheaper with a safety and reliability of operation greater than in the prior art.

The distance over which safety is ensured as the shell leaves the gun is increased due to the delaying action of sleeve 6 that must be pulled by the strip during the unwinding thereof.

What I claim is:

1. For use on a spinning projectile to be fired from a gun, an improved fuze comprising:

a fuze body to be fixed on the projectile,

an axial firing member movable longitudinally in said fuze body, and

means releasable with a delay after the firing of the projectile interposed between said firing member and said body for locking said firing member against longitudinal movement thereof in said body, said means consisting of, as sole and exclusive active element thereof, a spiral wound strip acting as an axial abutment by one of its edges and capable of unwinding in response to the spinning movement of the projectile to make said locking means inoperative, wherein the improvement comprises, an annular piece of substantial inertia interposed between said spiral strip and said firing member at a location where said annular piece ofiers substantially no resistance to the longitudinal movement of said axial firing member, said annular piece being freely rotatable about said firing member and being con- 4 nected in rotation with said spiral strip by fixation means released at the end of the unwinding of said spiral strip, said annular piece constituting means for slowing down the unwinding of said strip.

2. A fuze according to claim 1 comprising means for securing the inner end of said strip to said annular piece, said means being releasable by the centrifugal movement of said strip inner end away from said sleeve.

3. A fuze according to claim 2 wherein said annular piece is provided with a groove parallel to the axis thereof and the inner end of said strip is bent to engage in a radially slidable manner in said groove.

4. An improved fuze in accordance with claim 1 wherein said annular piece comprises a continuou's cylindrical sleeve longitudinally movable with said axial firing member upon unlocking of said firing member.

5. For use on a spinning projectile to be fired from a gun, a fuze which comprises, in combination:

a fuze body to be fixed on the projectile, said body being provided with an axial bore and forming an annular shoulder coaxially surrounding said bore,

a firing pin longitudinally slidable in said axial bore, said firing pin having an annular shoulder coaxial with said bore,

a sleeve coaxially surrounding said firing pin and freely rotatable about it, said sleeve being longitudinally movable with said pin and including an outward flange fitting against said firing pin shoulder, and

a strip spiral wound about said sleeve to form spires having their edges bearing against the respective flat faces of said body shoulder and of said sleeve flange, said strip constituting the sole and exclusive means for locking said firing pin against longitudinal movement thereof,

the outer wall of the cylindrical portion of said sleeve being provided with a longitudinal radial slot and the inner end of said strip being bent to engage freely in said longitudinal slot, the engagement between said strip and said sleeve being released upon unwinding of said strip, said sleeve constituting means for retarding the unwinding of said strip, and

said fuze body forming a cylindrical casing around said strip of sufficient radius to permit outward movement of the whole of said strip under the effect of the centrifugal force when said body is spinning about its axis.

6. A point detonating fuze according to claim 5 wherein said body shoulder is at the rear of said firing pin shoulder.

7. A base detonating fuze according to claim 5 wherein said body shoulder is at the front of said firing pin shoulder.

References Cited UNITED STATES PATENTS 3,022,733 2/1962 Junghans et al. 10279 X 3,076,410 2/1963 Guerne 102-79 3,270,670 9/1966 Guerne 102-79 FOREIGN PATENTS 1,183,409 12/1964 Germany.

BENJAMIN A. BORCHELT, Primary Examiner. GERALD H. GLANZMAN, Assistant Examiner.

US. Cl. X.R. 102-79, 82 

